The present invention relates to an optical switch and, more particularly, to an optical switch having a technique for confirming whether a switching operation is correctly performed in the optical switch used to switch an optical path.
As is well known, in the optical communication system, for example, when a plurality of optical lines each made of an optical fiber are to be tested, test light must be input to each line by sequentially switching the lines. In this case, an optical switch has conventionally been used.
The optical switch used for the above purpose has a plurality of light guides for inputting/outputting light, and is constituted such that a specific light guide can be selectively coupled to another designated light guide.
FIG. 10 shows the mechanism portion of a conventional optical switch for mechanically changing the direction of the optical axis of a specific light guide to switch the optical path.
In this optical switch, the tip of one optical fiber collimator (prepared by arranging a lens at the tip of the fiber) 1 constituting the specific optical guide is rotated by a stepping motor 2 every predetermined angle .alpha..
Remaining optical fiber collimators 3.sub.1, 3.sub.2, . . . , 3.sub.n are laid out such that the optical axis of each optical fiber collimator 3 coincides with the optical axis of the optical fiber collimator 1 at every interval of the predetermined angle .alpha..
By supplying, to the stepping motor 2, a pulse signal necessary for rotating the optical fiber collimator 1 through an angle N.multidot..alpha. (N is an integer), the optical fiber collimator 1 can be optically coupled to an arbitrary one of the remaining optical fiber collimators 3.sub.1, 3.sub.2, . . . , 3.sub.n.
In the optical switch using, as a driving source, the stepping motor 2 which rotates through an accurate rotation angle in accordance with an electrical (pulse) signal supplied in the above manner, an error may occur in the stepping motor itself, a circuit for supplying a driving pulse to the stepping motor, or the like.
In this case, even if the optical axis of the specific optical fiber collimator 1 does not coincide with that of a desired optical fiber collimator 3, this cannot be externally known.
When, therefore, this optical switch is used to test many optical lines, as described above, an erroneous test may be performed.
Another conceivable method is to detect the intensity of light passing through the optical fiber collimator.
In this case, however, the light intensity must be measured at a connection portion between the optical fiber collimator and the optical line in order to measure the intensity of test light in a test system of testing the optical line made of an optical fiber.
For this reason, measurement of the light intensity adversely affects an optical line test.